. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. ^Pigment Cup (Shield) Photoreceptive CelK / ~~/~ Outer and Inner Vitreous Bodies A B Fig. 720. Photoreceptors of amphioxus. a, sagittal section through ventral part of spinal cord showing light receptor cells in situ; b, a light cell and its shield (pigment cup), showing nerve endings surrounding the so-called vitreous bodies of the cell. (From Kappers, Huber and Crosby, The Comparative Anatomy of the Nervous System of Verte- brates, including Man, copyrig
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. ^Pigment Cup (Shield) Photoreceptive CelK / ~~/~ Outer and Inner Vitreous Bodies A B Fig. 720. Photoreceptors of amphioxus. a, sagittal section through ventral part of spinal cord showing light receptor cells in situ; b, a light cell and its shield (pigment cup), showing nerve endings surrounding the so-called vitreous bodies of the cell. (From Kappers, Huber and Crosby, The Comparative Anatomy of the Nervous System of Verte- brates, including Man, copyright 1936, by permission of The Macmillan Company, publishers.) (b) Cyclostomes.—The eyes of cyclostomes are degenerate rather than primitive. The eyeball is for the most part small and buried under a thick skin. It lacks cornea, iris, lens, lids, and ciliary apparatus, although Geotria macrophthalmus, a fresh-water cyclostome from South America, having unusually large eyes as its name indicates, is an exception. There is no differentiation into rods and cones in the retina, for only elongated rods are present, indicating that rods, which are adapted for the reception of lights, shadows, and the movements of external objects rather than for the reception of colors, are phylogenetically older than cones. (c) Fishes.—The elasmobranch eye is provided with a large rounded cornea, that aids the spherical lens in focusing. Partial compensation for the difficulty in seeing both forward and backward with an eye placed on the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
